Nitride semiconductor light emitting device and manufacturing method thereof

ABSTRACT

The light emitting device includes a p type nitride semiconductor layer, a light emitting layer and an n type nitride semiconductor layer stacked on an Si (silicon) substrate in this order from the side of the Si substrate. The Si substrate is partially removed to expose a part of the p type nitride semiconductor layer. On the exposed region of the p type nitride semiconductor layer, a p type electrode is formed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a nitride semiconductor light emittingdevice capable of emitting light in blue to ultraviolet regions and,more specifically, to a structure of a nitride semiconductor lightemitting device using an Si substrate.

2. Description of the Background Art

Conventionally, it has been known that a nitride semiconductor lightemitting device may be used as a blue light emitting device. Recently,blue light emitting diodes and violet semiconductor laser have beenstudied. FIG. 11 shows a schematic structure of a nitride semiconductorlight emitting device disclosed in Japanese Patent Laying-Open No.2001-7395. The nitride semiconductor light emitting device has such astructure in that on an Si substrate 100, a lower clad layer 200 of an ntype nitride semiconductor, a light emitting layer 300 and an upper cladlayer 400 of a p type nitride semiconductor are stacked in this order,with a p type ohmic electrode 500 formed on upper clad layer 400 and ann type ohmic electrode 600 formed on Si substrate 100.

Consider the structure of the nitride semiconductor light emittingdevice disclosed in Japanese Patent Laying-Open No. 2001-7395 in which an type nitride semiconductor layer and a p type nitride semiconductorlayer are stacked successively on Si substrate. When a current blockingstructure or a current constricting structure is to be formed in orderto improve light emitting efficiency in the light emitting device, it isnecessary to form an insulating film or a current blocking film, on a ptype nitride semiconductor layer, which is doped with Mg (magnesium),thin and has high resistivity.

Therefore, conventionally, the p type nitride semiconductor layer isdamaged when the insulating film or the current blocking film is formed,resulting in crystal defects generated in the p type nitridesemiconductor layer, which crystal defects capture Mg. Further, in mostcases, the insulating film contains oxygen, and the oxygen introduced tothe surface and to the inside of the p type nitride semiconductor layeroxidizes Mg. Therefore, concentration of Mg as the impurity in the ptype nitride semiconductor layer decreases, further increasing theresistivity and deteriorating characteristics of the light emittingdevice.

Further, when the insulating film or the current blocking film is to beformed on the p type nitride semiconductor layer as described above, thestep of fabrication of such a film is necessary.

Because of these problems, it has been difficult to form a currentblocking structure or a current constricting structure in the lightemitting device.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is tofabricate a current blocking structure or a current constrictingstructure easily in a light emitting device, and to fabricate a highlyreliable nitride light emitting device.

The above described object can be attained by the nitride semiconductorlight emitting device in accordance with the present invention thatincludes a p type nitride semiconductor layer, a light emitting layerand an n type nitride semiconductor layer stacked on an Si (silicon)substrate in this order from the Si substrate, wherein the Si substrateis partially removed to expose a part of the p type nitridesemiconductor layer, and on the exposed region of p type nitridesemiconductor layer, a p type electrode is formed.

In the nitride semiconductor light emitting device of the presentinvention, an n type pad electrode may be formed at a corner on thesurface of the n type nitride semiconductor layer.

In the nitride semiconductor light emitting device of the presentinvention, the p type nitride semiconductor layer may include a regionhaving high dopant concentration and a region having low dopantconcentration.

In the nitride semiconductor light emitting device of the presentinvention, the backside of the Si substrate opposite to the surfacehaving the stack formed thereon is partially removed to have a recessedor protruded shape, and the surface of the p type nitride semiconductorlayer may be exposed at the removed region.

In the nitride semiconductor light emitting device of the presentinvention, when the back side of Si substrate opposite to the surfacehaving the stack formed thereon is partially removed to have a recessedshape, a reflective film is formed at the recessed portion.

Further, in the nitride semiconductor light emitting device of thepresent invention, when the backside of the Si substrate opposite to thesurface having the stack formed thereon is partially removed to have aprotruded shape, the n type nitride semiconductor layer may be formed tohave a protruded shape. Further, in this case, an n type pad electrode,or an n type pad electrode and an n type light emitting electrode may beformed at the top of the protruding portion of n type nitridesemiconductor layer.

In the nitride semiconductor light emitting device of the presentinvention, that region of the p type nitride semiconductor layer whichis positioned on the region where the Si substrate is removed may havehigher dopant concentration than other regions of the p type nitridesemiconductor layer.

In the nitride semiconductor light emitting device of the presentinvention, the Si substrate is non-conductive, and it may be non-lighttransmitting.

Further, the present invention provides a method of manufacturing anitride semiconductor light emitting device, including the steps ofstacking a p type nitride semiconductor layer, a light emitting layerand an n type nitride semiconductor layer in this order on an Sisubstrate to form a stacked body; removing a part of the Si substrate;exposing the surface of the p type nitride semiconductor layer from theportion where the Si substrate is removed; heat-treating the stackedbody with part of the Si substrate removed; and forming a p typeelectrode on the exposed surface of the p type nitride semiconductorlayer.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 8 are schematic cross sections of the nitride semiconductorlight emitting device fabricated in accordance with first to eighthembodiments of the present invention.

FIG. 9A is a schematic cross section of the nitride semiconductorstacked body in accordance with the first to eighth embodiments of thepresent invention.

FIG. 9B represents dividing lines for fabricating the nitridesemiconductor stacked body of the first to eighth embodiments.

FIGS. 10A and 10B represent schematic back surface of the substrate ofthe nitride semiconductor light emitting device in accordance with thefirst to eighth embodiments of the present invention.

FIG. 11 is a schematic cross section of the nitride semiconductor lightemitting device disclosed in Japanese Patent Laying-Open No. 2001-7395.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail in thefollowing. It is noted, however, that the present invention is notlimited to these embodiments.

First Embodiment

FIG. 1 shows a structure of a nitride semiconductor light emittingdevice in accordance with the first embodiment, in which a p typenitride semiconductor layer 2 doped with Mg, a light emitting layer 3and an n type nitride semiconductor layer 4 are stacked in this order ona non-conductive substrate 1 of Si. On the back surface ofnon-conductive substrate 1 opposite to the surface having the stackformed thereon, the non-conductive substrate 1 is formed to have aprotruded shape. On surfaces of the protruded non-conductive substrate 1and p type nitride semiconductor layer 2, a p type electrode 7 isformed. Approximately at the center of the surface of n type nitridesemiconductor layer 4, an n type pad electrode 6 is formed.

When the nitride semiconductor light emitting device shown in FIG. 1 isfabricated, first, the non-conductive substrate 1 is set in a growthapparatus for MOCVD (Metal Organic Chemical Vapor Deposition), forexample, and p type nitride semiconductor layer 2, light emitting layer3 and n type nitride semiconductor layer 4 are stacked on thenon-conductive substrate 1 successively.

Thereafter, the stacked body is taken out from the apparatus, and anunnecessary portion of non-conductive substrate 1 is removed by using ahydrogen fluoride based etchant, so as to process non-conductivesubstrate 1 to have a protruded shape. Here, the diameter at the root ofthe protruding portion is set to 150 μm.

Thereafter, n type pad electrode 6 and p type electrode 7 are formed.The n type pad electrode 6 is formed by stacking a Hf (hafnium) layerhaving the thickness of 10 nm and an Al (aluminum) layer having thethickness of 1000 nm thereon, approximately at the center on the surfaceof n type nitride semiconductor layer 4. The p type electrode 7 isformed by stacking a Pd (palladium) layer having the thickness of 20 nmand an Au (gold) layer having the thickness of 1000 nm thereon, to coverthe surfaces of the protruded non-conductive substrate 1 and p typenitride semiconductor layer 2.

Thereafter, the light emitting devices fabricated in the above describedmanner are divided into rectangles each of 300 μm square. Each of thethus obtained light emitting devices is mounted on a lead frame, withthe p type electrode 7 facing the bottom portion of a cup.

FIG. 9A schematically shows the stacked body of the nitridesemiconductor in accordance with the present invention. FIG. 9B shows adividing line 13 b for dividing the nitride semiconductor light emittingdevices in accordance with the present invention.

The nitride semiconductor light emitting device in accordance with thefirst embodiment fabricated in the above described manner is fabricatednot by stacking an n type nitride semiconductor layer 4 on thenon-conductive substrate 1 as in the prior art, but fabricated bystacking a p type nitride semiconductor layer 2. Therefore, differentfrom the prior art, it is unnecessary to newly form an insulating filmor the like on p type nitride semiconductor layer 2. Therefore, thecrystal defects in p type nitride semiconductor layer 2 generated whenthe insulating film or the like is formed can be reduced. Therefore,diffusion of Mg doped in p type nitride semiconductor layer 2 to thelight emitting layer at the time of conduction can be suppressed, andhence a nitride semiconductor light emitting device having superiorreliability can be fabricated.

Further, as the substrate 1 is non-conductive, the amount of currentflowing to the semiconductor region stacked on that portion wheresubstrate 1 has been removed becomes larger than the amount of currentflowing to the semiconductor region stacked on the portion where thesubstrate is not removed, when current is introduced from the outside tothe light emitting device. Therefore, the semiconductor region throughwhich the current flows can be biased. Therefore, it is unnecessary tonewly provide a current blocking structure or a current constrictingstructure.

Second Embodiment

In the structure of the nitride semiconductor light emitting device inaccordance with the second embodiment shown in FIG. 2, a p type nitridesemiconductor layer 2, a light emitting layer 3 and an n type nitridesemiconductor layer 4 are stacked in this order on a non-conductivesubstrate 1 of Si. On the backside of non-conductive substrate 1opposite to the surface having the stack formed thereon, thenon-conductive substrate 1 is formed to have a recessed shape, and thereis an opening 8 at the portion where non-conductive substrate 1 isremoved. Further, on the surfaces of non-conductive substrate 1 and ptype nitride semiconductor layer 2, a p type electrode 7 is formed, andan n type pad electrode 6 is formed at a corner on the surface of n typenitride semiconductor layer 4.

FIG. 10A shows the shape of the back surface of non-conductive substrate1 of the nitride semiconductor light emitting device in accordance withthe present embodiment. Referring to FIG. 10A, there are openings 8 onthe back surface of non-conductive substrate 1, and along dividing lines13, the wafer is cut into chips (semiconductor light emitting devices).

When the nitride semiconductor light emitting device shown in FIG. 2 isto be fabricated, first, the non-conductive substrate 1 is set in agrowth apparatus for MOCVD, for example, and p type nitridesemiconductor layer 2 doped with Mg, light emitting layer 3 and n typenitride semiconductor layer 4 are stacked on the non-conductivesubstrate 1 successively.

Thereafter, the stacked body is taken out from the apparatus,unnecessary portion of non-conductive substrate 1 is removed by using ahydrogen fluoride based etchant, and a recessed opening 8 is formed.Here, the diameter of the recessed opening 8 is set to 150 μm.

Thereafter, the stacked body is introduced into a heat treatmentfurnace, the stacked body is placed on a susceptor of the heat treatmentfurnace with the side of non-conductive substrate 1 facing upward, andthe stacked body is held in a nitrogen atmosphere at 800° C. for 5minutes for heat treatment.

Thereafter, the stacked body is taken out from the heat treatmentfurnace, and n type light transmitting electrode 5, n type pad electrode6 and p type electrode 7 are formed. The n type light transmittingelectrode 5 is formed by forming an ITO (Sn added In₂O₃) to thethickness of 100 nm on the surface of n type nitride semiconductor layer4. The n type pad electrode 6 is formed by stacking a Hf layer havingthe thickness of 20 nm and further an Au layer having the thickness of1000 nm thereon, at opposing ends on the surface of n type nitridesemiconductor layer 4. The p type electrode 7 is fabricated by stackinga Pd layer having the thickness of 20 nm and an Au layer having thethickness of 1000 nm thereon, on the surfaces of non-conductivesubstrate 1 and p type nitride semiconductor layer 2.

The light emitting devices fabricated in this manner are divided intorectangles each of 300 μm square as shown in FIG. 10A, and the devicesare each mounted on a lead frame with the side of p type electrode 7facing the bottom portion of the cup.

FIG. 9A is a schematic cross section of the stacked body of the lightemitting devices fabricated in the above described manner, and FIG. 9Brepresent dividing line 13 a for dividing and fabricating each lightemitting device.

Referring to FIG. 2, in the light emitting device of the presentembodiment, as the stacked body is heat-treated in the above describedmanner, the p type nitride semiconductor layer 2 comes to have a region2A having high concentration and a region 2B having low concentration ofMg doped in p type nitride semiconductor layer 2. The reason for this isthat Si in non-conductive substrate 1 enters the p type nitridesemiconductor layer 2 to compensate for p type dopant and further that,when Mg is bonded to H (hydrogen) during crystal growth andnon-conductive substrate 1 exists on p type nitride semiconductor layer2, H cannot go outside the p type nitride semiconductor layer 2 evenafter heat treatment, and therefore, at that region of p type nitridesemiconductor layer 2 which corresponds to the region wherenon-conductive substrate 1 exists comes to have high resistivity.Therefore, in region 2A, the resistivity becomes 2 to 6 Ωcm, that is,lower than in region 2B of which resistivity is 10⁶ Ωcm.

Further, as the substrate is non-conductive, the amount of currentflowing to the region 2A stacked on the portion where the substrate isremoved becomes larger than the amount of current flowing to region 2Bstacked on the portion where the substrate is not removed, when thecurrent is introduced from the outside to the light emitting device.

Therefore, the current introduced to the light emitting device isconcentrated at light emitting layer 3A positioned on the region 2A, andthe current hardly flows to the light emitting layer 3B positioned onthe region 2B. Therefore, the light emitting device can exhibit currentconstricted type light emitting characteristic.

Therefore, light emitting layer 3B positioned above non-conductivesubstrate 1 that absorbs the light generated by the light emittingdevice hardly emits light in the light emitting device of the presentembodiment. Therefore, as compared with the prior art, efficiency oflight emission to the outside of the light emitting device can beimproved.

Third Embodiment

In the structure of the nitride semiconductor light emitting device inaccordance with the third embodiment shown in FIG. 3, a p type nitridesemiconductor layer 2 doped with Mg, a light emitting layer 3 and an ntype nitride semiconductor layer 4 are stacked in this order on anon-conductive substrate 1 of Si. The back surface of non-conductivesubstrate 1 opposite to the surface having the stack formed thereon isformed to have a protruded shape. There is an opening 8 wherenon-conductive substrate 1 is removed. On the surfaces of protrudednon-conductive substrate 1 and p type nitride semiconductor layer 2, a ptype electrode 7 is formed. An n type light transmitting electrode 5 isformed approximately on the entire surface of n type nitridesemiconductor layer 4, and an n type pad electrode 6 is formedapproximately at the center of the surface of n type nitridesemiconductor layer 4.

FIG. 10B shows the shape of the back surface of non-conductive substrate1, of the nitride semiconductor light emitting devices in accordancewith the present embodiment. Referring to FIG. 10B, there are openings 8on the side of the back surface of non-conductive substrate 1, and thewafer is divided into chips (semiconductor light emitting devices) alongdividing lines 13.

When the nitride semiconductor light emitting device of FIG. 3 is to befabricated, first, non-conductive substrate 1 is set in a growthapparatus for MOCVD, for example, and p type nitride semiconductor layer2, light emitting layer 3 and n type nitride semiconductor layer 4 arestacked on the non-conductive substrate 1 successively.

Thereafter, the stacked body is taken out from the apparatus, and anunnecessary portion of non-conductive substrate 1 is removed by using ahydrogen fluoride based etchant, so that the substrate 1 is processed tohave a protruded shape. Here, the diameter of the protruded portion ofnon-conductive substrate 1 is set to 150 μm.

Thereafter, the stacked body is introduced to a heat treatment furnace,the stacked body is placed on a susceptor of the heat treatment furnacewith the side of non-conductive substrate 1 facing upward, and thestacked body is held in a nitrogen atmosphere at 800° C. for 2 minutesfor heat treatment.

Thereafter, the stacked body is taken out from the heat treatmentfurnace, and n type light transmitting electrode 5, n type pad electrode6 and p type electrode 7 are formed. The n type light transmittingelectrode 5 is fabricated by forming ITO to the thickness of 50 nm onthe surface of n type nitride semiconductor layer 4. The n type padelectrode 6 is fabricated by forming an Au layer having the thickness of1500 nm approximately at the center of the surface of n type nitridesemiconductor layer 4. The p type electrode 7 is fabricated by stackinga Pd layer having the thickness of 50 nm and further an Au layer havingthe thickness of 2000 nm thereon, to cover the surfaces of the protrudednon-conductive substrate 1 and p type nitride semiconductor layer 2.

Thereafter, the light emitting devices fabricated in the above describedmanner are divided into rectangles each of 300 μm square along thedividing lines 13 as shown in FIG. 10B. Each of the resulting lightemitting devices is mounted on a lead frame with the side of p typeelectrode 7 facing the bottom portion of the cup.

FIG. 9A schematically shows the cross section of the stacked body of thelight emitting device fabricated in the above described manner, and FIG.9B shows the dividing line 13 b for dividing and fabricating the lightemitting devices.

Referring to FIG. 3, the stacked body of the light emitting device inaccordance with the present embodiment is also subjected to heattreatment, and therefore, p type semiconductor layer 2 comes to have aregion 2A having high concentration and a region 2B having lowconcentration of Mg doped in p type semiconductor layer 2.

Further, as substrate 1 is non-conductive, the amount of current flowingto a region 2A can be larger than the amount of current flowing toregion 2B.

Therefore, the current introduced to the light emitting device isconcentrated at light emitting layer 3A positioned on region 2A, and thecurrent hardly flows to light emitting layer 3B positioned on region 2B.Thus, the light emitting device can exhibit the current blocking typelight emitting characteristic.

Therefore, in the light emitting device in accordance with the presentembodiment, the light emitting layer 3B positioned above non-conductivesubstrate 1 that absorbs the light generated by the light emittingdevice hardly emits light. Therefore, as compared with the prior art,the efficiency of light emission to the outside of the light emittingdevice can be improved.

Fourth Embodiment

In the structure of the nitride semiconductor light emitting device inaccordance with the fourth embodiment shown in FIG. 4, a p type nitridesemiconductor layer 2 doped with Mg, a light emitting layer 3 and an ntype nitride semiconductor layer 4 are stacked in this order on anon-conductive substrate 1 of Si. There is an opening 8 where thenon-conductive substrate 1 is removed. Further, on surfaces ofnon-conductive substrate 1 and p type nitride semiconductor layer 2, a ptype light transmitting electrode 70 is formed. At a corner of p typelight transmitting electrode 70, a p type pad electrode 71 is formed. Areflecting electrode 51 serving as a reflective layer is formedapproximately on the entire surface of n type nitride semiconductorlayer 4, and an n type pad electrode 6 is formed on reflecting electrode51.

Here, the p type light transmitting electrode 70 formed on the surfacesof non-conductive substrate 1 and p type nitride semiconductor layer 2is a Pd thin film having the thickness of 5 nm. The reflecting electrode51 may be formed by stacking a Hf layer having the thickness of 50 nmand further an Al layer having the thickness of 2000 nm thereon.

The nitride semiconductor light emitting device shown in FIG. 4 may befabricated in the similar manner as the second embodiment.

Referring to FIG. 4, the light emitting device in accordance with thepresent embodiment is also subjected to heat treatment of the stackedbody. Therefore, the p type nitride semiconductor layer 2 comes to havea region 2A having high concentration and a region 2B having lowconcentration of Mg doped in p type nitride semiconductor layer 2.

Further, as substrate 1 is non-conductive, the amount of current flowingto region 2A can be larger than the amount of current flowing to region2B.

Therefore, the current introduced to the light emitting deviceconcentrates at the light emitting layer 3A positioned on region 2A, andthe current hardly flows to light emitting layer 3B positioned on region2B. Therefore, the light emitting device can exhibit the currentconstricting type light emitting characteristic.

Further, in the present embodiment, the device is mounted on the leadframe with the side of n type pad electrode 6 facing the bottom portionof the cup. Thus, the generated light is reflected by reflectingelectrode 51 positioned above light emitting layer 3A, so that theemitted light can further be drawn to the outside of the light emittingdevice through opening 8 with a Pd thin film provided thereon.Therefore, the efficiency of light emission to the outside can beimproved by the present embodiment, as compared with the secondembodiment.

Fifth Embodiment

The structure of the nitride semiconductor light emitting device inaccordance with the fifth embodiment shown in FIG. 5, a multi-layeredstacked body including p type nitride semiconductor layers 20 and 21doped with Mg, a light emitting layer 3 and an n type nitridesemiconductor layer 4 are stacked in this order on non-conductivesubstrate 1 of Si. There is an opening 8 where non-conductive substrate1 is removed. Further, on surfaces of non-conductive substrate 1 and themulti-layered stacked body, a p type electrode 7 is formed. Further, ann type light transmitting electrode 5 is formed approximately on theentire surface of n type nitride semiconductor layer 4, and n type padelectrodes 6 are formed at opposing end portions on the surface of ntype nitride semiconductor layer 4.

The nitride semiconductor light emitting device shown in FIG. 5 may befabricated in the similar manner as the second embodiment.

Referring to FIG. 5, the light emitting device of the present inventionis also subjected to the heat treatment of the stacked body. Therefore,the multi-layered stacked body including p type nitride semiconductorlayers 20 and 21 comes to have a region 2A having high concentration anda region 2B having low concentration of Mg doped in the multi-layeredstacked body including p type nitride semiconductor layers 20 and 21.

Further, as substrate 1 is non-conductive, the amount current flowing toregion 2A can be larger than the amount of current flowing to region 2B.

Therefore, the current introduced to the light emitting device isconcentrated at the light emitting layer 3A positioned on region 2A ofmulti-layered stacked body including p type nitride semiconductor layers20 and 21. The current hardly flows to the light emitting layer 3Bpositioned on region 2B. Thus, the light emitting device can exhibit thecurrent constricting type light emitting characteristic.

Further, in the present embodiment, the multi-layered staked bodyincluding p type nitride semiconductor layers 20 and 21 is amulti-layered film of nitride semiconductor formed of 42 layers of acomposite comprising a GaN layer 20 and Al_(0.34)Ga_(0.66)N layer 21.The thickness of the film is an integer multiple of ¼ of the lightemission wavelength.

Therefore, the multi-layered stacked body including the aforementioned ptype nitride semiconductor layers 20 and 21 functions as a reflectivelayer in the present embodiment, and reflects the emitted light abovethe light emitting device. Therefore, the light that proceeds tonon-conductive substrate 1 of Si, which serves as a light absorber,decreases, and therefore the efficiency of light emission to the outsidecan be improved.

Sixth Embodiment

In the structure of the nitride semiconductor light emitting device inaccordance with the sixth embodiment shown in FIG. 6, a p type nitridesemiconductor layer 2, doped with Mg, a light emitting layer 3 and an ntype nitride semiconductor layer 4 are stacked in this order on anon-conductive substrate 1 of Si. Further, the back surface ofnon-conductive substrate 1 opposite to the surface having the stackedbody formed thereon is formed to have a resecced shape. There is anopening 8 where the non-conductive substrate 1 is removed. On surfacesof non-conductive substrate 1 and p type nitride semiconductor layer 2,a p type electrode 7 is formed. Further, an n type light transmittingelectrode 5 is formed on the surface of n type nitride semiconductorlayer 4. An n type pad electrode 6 is formed at a corner of the surfaceof n type nitride semiconductor layer 4, and there is an opening 9 wherenothing is formed, on the surface of n type nitride semiconductor layer4.

Referring to FIG. 6, the light emitting device of the present embodimentis also subjected to heat treatment of the stacked body. Therefore, ptype semiconductor layer 2 comes to have a region 2A having highconcentration and a region 2B having low concentration of Mg doped in Ptype semiconductor layer 2.

Further, as substrate 1 is non-conductive, the amount of current flowingto region 2A can be larger than the amount of current flowing to region2B.

Therefore, the current introduced to the light emitting device isconcentrated at the light emitting layer 3A positioned on region 2A of ptype semiconductor layer, and the current hardly flows to light emittinglayer 3B positioned on region 2B. Therefore, the light emitting devicecan exhibit the current constricting type light emitting characteristic.

Further, in the light emitting device of the present embodiment, thereis an opening 9 where nothing is formed, on the surface of n typenitride semiconductor layer 4 as the light emitting surface. Namely,there is a region where the emitted light is not absorbed by n typelight transmitting electrode 5. Therefore, the efficiency of lightemission to the outside can be improved as compared with the secondembodiment.

Further, when the n type light transmitting electrode 5 is not formed inthe present embodiment, the efficiency of light emission to the outsidecan further be improved.

Seventh Embodiment

In the structure of the nitride semiconductor light emitting device inaccordance with the seventh embodiment shown in FIG. 7, a p type nitridesemiconductor layer 2 doped with Mg, a light emitting layer 3 and an ntype nitride semiconductor layer 4 are stacked in this order on anon-conductive substrate 1 of Si. A back surface of the non-conductivesubstrate 1 opposite to the surface having the stacked body formedthereon, the non-conductive substrate 1 is formed to have a protrudedshape. There is an opening 8 where the non-conductive substrate 1 isremoved. Further, n type nitride semiconductor layer 4 is formed to havea protruded shape, and an n type pad electrode 6 is formed at the top ofthe protrusion. Further, a p type electrode 7 is formed on surfaces ofthe protruded non-conductive substrate 1 and p type nitridesemiconductor layer 2.

Referring to FIG. 7, the light emitting device in accordance with thepresent embodiment is also subjected to heat treatment of the stackedbody. Therefore, the p type nitride semiconductor layer 2 comes to havea region 2A having high concentration and a region 2B having lowconcentration of Mg doped in p type nitride semiconductor layer 2.

Further, as substrate 1 is non-conductive, the amount of current flowingto region 2A can be larger than the amount of current flowing to region2B.

Therefore, the current introduced to the light emitting device isconcentrated at light emitting layer 3A positioned on region 2A of ptype nitride semiconductor layer, and the current hardly flows to lightemitting layer 3B positioned on region 2B. Therefore, the light emittingdevice can exhibit the current blocking type light emittingcharacteristic.

Therefore, in the light emitting device of the present embodiment also,light emitting layer 3B positioned above non-conductive substrate 1,which absorbs light emitted from the light emitting device, hardly emitslight. Therefore, the amount of light absorbed by non-conductivesubstrate 1 of Si, which is a light absorber, can be reduced as comparedwith the prior art, and the efficiency of light emission to the outsideof the light emitting device can be improved.

When n type nitride semiconductor layer 4 is formed to have portionsother than the protruded portion made thin by dry etching, theefficiency of light emission to the outside of the light emitting devicecan further be improved.

Eighth Embodiment

In the structure of the nitride semiconductor light emitting device inaccordance with the eighth embodiment shown in FIG. 8, a p type nitridesemiconductor layer 2 doped with Mg, a light emitting layer 3 and n typenitride semiconductor layer 4 are stacked in this order on anon-conductive substrate 1 of Si. Further, the back surface of thenon-conductive substrate 1 opposite to the surface having the stackedbody formed thereon, is formed to have a recessed shape, and there is anopening 8 where non-conductive substrate 1 is removed. On surfaces ofnon-conductive substrate 1 and p type nitride semiconductor layer 2, a ptype light transmitting electrode 70 is formed. Further, on the surfaceof p type light transmitting electrode 70, a ZrO₂ (zirconium oxide)layer 11 and an SiO₂ (silicon dioxide) layer 12 as dielectricmulti-layered reflecting film is formed. On the surface of n typenitride semiconductor layer 4, an n type light transmitting electrode 5is formed, and at opposing ends on the surface of n type nitridesemiconductor layer 4, n type pad electrodes 6 are formed. There is anopening 9 where nothing is formed, on the remaining surface of n typenitride semiconductor layer 4.

Referring to FIG. 8, the light emitting device of the present embodimentis also subjected to heat treatment of the stacked body. Therefore, ptype semiconductor layer 2 comes to have a region 2A having highconcentration and a region 2B having low concentration of Mg doped in ptype semiconductor layer 2.

Further, as substrate 1 is non-conductive, the amount of current flowingto region 2A can be larger than the amount of current flowing to region2B.

Therefore, the current introduced to the light emitting device isconcentrated at light emitting layer 3A positioned on region 2A of the ptype semiconductor layer, and the current hardly flows to light emittinglayer 3B positioned on region 2B. Therefore, the light emitting devicecan exhibit the current constricting type light emission characteristic.

Further, in the present embodiment, the dielectric multi-layeredreflecting film is formed of ZrO₂ layer 11 and SiO₂ layer 12, and thefilm thickness is an integer multiple of ¼ of the light emissionwavelength.

Therefore, in the present embodiment, the light generated near theregion of light emitting layer 3A and proceeding to non-conductivesubstrate 1 passes through p type light emitting electrode 70, isreflected by the dielectric multi-layered reflecting film functioning asa reflective layer formed on the surface of p type light emittingelectrode 70, and again proceeds to the inside of the light emittingdevice. Accordingly, the amount of light that proceeds to non-conductivesubstrate 1 of Si as a light absorber can be reduced, and hence theamount of light absorbed by non-conductive substrate 1 can be reduced ascompared with the prior art. Therefore, the efficiency of light emissionto the outside can be improved as compared with the prior art.

Further, similar effects can be attained even when the dielectricmulti-layered reflecting film is a semiconductor multi-layeredreflecting film.

The materials of the p type nitride semiconductor layer, the lightemitting layer and the n type nitride semiconductor layer included inthe nitride semiconductor light emitting device of the present inventionare not specifically limited. As an example, a nitride semiconductorrepresented by the expression In_(x)Al_(y)Ga_(1 . . . x . . . y)N (0≦x,0≦y, x+y≦1) may be used. As the light emitting layer, an MQW (multiplequantum well) light emitting layer or an SQW (single quantum well) lightemitting layer may be used. The dopant used for forming the p typenitride semiconductor layer and a n type nitride semiconductor layer isnot specifically limited.

Further, in the present invention, the p type nitride semiconductorlayer and the n type nitride semiconductor layer may include a singlelayer or multiple layers. The space between the layers is notspecifically limited. However, an integer multiple of ¼ of the lightwavelength is preferred.

In the present invention, the method of stacking the nitridesemiconductor layer and the like is not specifically limited. Forexample, MOCVD method may be used.

Further, in the present invention, the method of removing the substrateis not specifically limited. For example, dry etching method may beused.

In the present invention, materials of the n type electrode and the ptype electrode are not specifically limited. Ti, Hf, ITO, SnO₂, Ni or Pdor the like may be used for the n type electrode and the p typeelectrode.

In the present invention, the method of forming the p type electrode andthe n type electrode are not specifically limited, and a common methodmay be used.

In the present embodiment, it is possible to form a pad electrode forwire bonding or the like on the p type electrode, n type electrode, thep type semiconductor layer or on the substrate. The pad electrode isformed of a material such as Au, and formed by the method of vapordeposition, for example. To the pad electrode, a wire of Au or the likefor introducing external current, for example, may be bonded.

The device structure of the nitride semiconductor light emitting deviceof the present invention is applicable to any structure includinghomostructure, double hetero structure, single hetero structure, or astructure having a quantum well structure in an active layer.

The present invention, a p type nitride semiconductor layer, a lightemitting layer and an n type nitride semiconductor layer are stacked ona non-conductive substrate formed of Si or the like, in this order fromthe side of the non-conductive substrate, whereby current blocking typeand current constricted type nitride semiconductor light emittingdevices can be fabricated. Therefore, it becomes unnecessary to form aninsulator film or the like on the p type nitride semiconductor layer.Thus, crystal defects in the p type nitride semiconductor layer can bereduced as compared with the prior art, and a highly reliable nitridesemiconductor light emitting device can be fabricated.

Further, a light reflecting film is provided at a portion where thesubstrate is removed, so as to direct the light back to the inside ofthe light emitting device, whereby light can be emitted from a surfacedifferent from the substrate surface as the light absorbing body.Therefore, the efficiency of light emission to the outside can beimproved as compared with the prior art.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A nitride semiconductor light emitting device, comprising: a p-type nitride semiconductor layer; a light emitting layer; an n-type nitride semiconductor layer, where these three layers are stacked on an Si (silicon) substrate in this order from the side of the Si substrate; where Si substrate is partially removed to expose a part of the p-type nitride semiconductor layer, and on the exposed region of the p-type nitride semiconductor layer, a p-type electrode is formed.
 2. The nitride semiconductor light emitting device according to claim 1, wherein said p type nitride semiconductor layer includes a region having high dopant concentration and a region having low dopant concentration, wherein the region having high dopant concentration and the region having low dopant concentration are positioned laterally with respect to each other.
 3. The nitride semiconductor light emitting device according to claim 1, wherein a backside of said Si substrate opposite to the surface having the stack formed thereon is partially removed to have a recessed shape, and at the removed region, a surface of said p type nitride semiconductor layer is exposed.
 4. A nitride semiconductor light emitting device comprising a p type nitride semiconductor layer, a light emitting layer and an n type nitride semiconductor layer stacked on an Si (silicon) substrate in this order from the side of the Si substrate, wherein said Si substrate is partially removed to expose a part of the p type nitride semiconductor layer, and on the exposed region of the p type nitride semiconductor layer, a p type electrode is formed, wherein a backside of said Si substrate opposing to the surface having the stack formed thereon is partially removed to have a protruded shape, and at the removed region, a surface of said p type nitride semiconductor layer is exposed.
 5. The nitride semiconductor light emitting device according to claim 1, wherein a region of the p type nitride semiconductor above the region where said Si substrate is removed has dopant concentration higher than that of other regions of the p type nitride semiconductor layer, wherein the region having higher dopant concentration and the other regions are positioned laterally with respect to each other.
 6. The nitride semiconductor light emitting device according to claim 1, wherein an n type pad electrode is formed at a corner of a surface of the n type nitride semiconductor layer stacked above said Si substrate.
 7. A nitride semiconductor light emitting device comprising a p type nitride semiconductor layer, a light emitting layer and a n type nitride semiconductor layer stacked on an Si(silicon) substrate in this order from the side of the Si substrate, wherein said Si substrate is partially removed to expose a part of the p type nitride semiconductor layer, and on the exposed region of then type nitride semiconductor layer, a p type electrode is formed wherein a reflective film is formed at a recessed portion where said Si substrate is partially removed.
 8. A nitride semiconductor light emitting device comprising a p type nitride semiconductor layer, a light emitting layer and an n type nitride semiconductor layer stacked on an Si (silicon) substrate an this order from the side of the Si substrate, wherein said Si substrate is partially removed to expose a part of the p type nitride semiconductor layer, and on the exposed region of the p type nitride semiconductor layer, a p type electrode is formed, wherein said Si substrate is partially removed to have a protruded shape, and said n type nitride semiconductor layer is formed to have a protruded shape.
 9. The nitride semiconductor light emitting device according to claim 8, wherein an n type pad electrode or an n type pad electrode and an n type light transmitting electrode are formed at a top portion of the protrusion of said n type nitride semiconductor layer.
 10. A nitride semiconductor light emitting device comprising a p type nitride semiconductor layer, a light emitting layer and an n type nitride semiconductor layer stacked on an Si (silicon) substrate in this order from the side of the Si substrate, wherein said Si substrate is partially removed to expose a part of the p type nitride semiconductor layer, and on the exposed region of the p type nitride semiconductor layer, a p type electrode is formed, wherein said Si substrate is non-conductive and non light-transmitting.
 11. A nitride semiconductor light emitting device, comprising a p type nitride semiconductor layer, a light emitting layer and an n type nitride semiconductor layer stacked on an Si (silicon) substrate in this order from the side of the Si substrate, wherein said Si substrate is partially removed to expose a part of the p type nitride semiconductor layer, and on the exposed region of the p type nitride semiconductor layer, a p type electrode is formed, wherein a region of the p type nitride semiconductor layer above said Si substrate has higher resistivity than the resistivity of another region of the p type nitride semiconductor layer.
 12. A nitride semiconductor light emitting device, comprising a p type nitride semiconductor layer, a light emitting layer and an n type nitride semiconductor layer stacked on an Si (silicon) substrate in this order from the side of the Si substrate, wherein said Si substrate is partially removed to expose a part of the p type nitride semiconductor layer, and on the exposed region of the p type nitride semiconductor layer, a p type electrode is formed, wherein a region of the p type nitride semiconductor layer corresponding to an opening where said Si substrate is removed has lower resistivity than the resistivity of another region of the p type nitride semiconductor layer. 